SharePoint: How to find out if you have legacy add-ins that are affected by the SharePoint Add-in model retirement

Question

How to find out if my SharePoint Online tenant has legacy add-ins that stop working when the legacy add-in model is retiring?

Answer

In order to list add-ins, you can use few techniques:

• SharePoint REST API
• PnP CSOM
• PnP PowerShell
• CLI for Microsoft 365

Easiest in my opinion is the CLI for Microsoft 365, as it will give you the result in just a two commands.  If you wish to build further automation, you will want to pick the PnP PowerShell library to use in your PowerShell script or the PnP CSOM if you're using .NET.

To get a quick list or add-ins using the CLI for Microsoft 365, first login to your tenant with command:

m365 login

then list the add-ins with command:

m365 spo app list

in order to output the add-in JSON array to a file, use command:

m365 spo app list > add-ins.json

The output will contain array of add-ins, and the property IsClientSideSolution will tell you if the application is legacy and will be retiring. 

If IsClientSideSolution is false, it is legacy and will be retired.

If IsClientSideSolution is true, it is modern and will NOT be retired.